A few weeks ago, Offer created his first rail puzzle for the system in London, where he lives. He got a good response so he made puzzles for other cities. "I find it really interesting as a concept as you really need to know the city to even have a chance of playing the game," Offer said in an e-mail.

Chicago's system matched the format of his game "quite well," he said. Offer told RedEye he has not been to Chicago.

The University of Illinois' rescinded job offer to a professor and a controversy over a faculty blog at Chicago State University helped land the two schools on a 2014 "worst of" list for student and faculty free speech rights.